Device for supplying fuel to the atomisers of a combustion engine

ABSTRACT

A device for supplying fuel to the atomisers of a combustion engine comprising a fuel pump the inlet of which communicates with a fuel tank and the outlet of which, where during operation a constant pressure is maintained by a pressure control device, communicates with the inlet of a flow restrictor having a passage which can be controlled continuously between the fully opened and the fully closed condition by an electrically controlled operating element, the restrictor outlet communicating with the fuel inlet chamber of a pressure control valve which during operation maintains a constant pressure at the restrictor outlet which is lower than the constant pressure at the restrictor inlet and the fuel outlet chamber of said valve communicates with a fuel distributor which is capable of communicating the various atomizers periodically and per atomizers always for the same time interval with said fuel outlet chamber.

United States Patent 191 Kleuters Apr. 9, 1974 [75] lnventor: Wilhelm Josef Kleuters,

Emmasingel, Netherlands [73] Assignee: U.S. Philips Corporation, New

York, NY.

221 Filed: Nov. 1, 1971 [21] Appl.No.: 194,183

[30] Foreign Application Priority Data Nov. 14, 1970 Netherlands 7016724 521 U.S.Cl. 137/116, 239/126 51 Int. Cl. G05d 11/00 v [58] Field of Search 137/116; 239/126, 127

[56] References Cited UNITED STATES PATENTS 3,083,721 4/1963 Matthews 137/613 X 3,362,643 Larson et al 137/116 X FOREIGN PATENTS OR APPLlCATlONS 211,459 10/1960 Austria 137/116 1,148,076 6/1957 France 137/116 1,342,743 9/1963 France 137/116 Primary Examiner-William R. Cline Attorney, Agent, or Firm-Frank R. Trifari [57] ABSTRACT A device for supplying fuel to the atomisers of a combustion engine comprising a fuel pump the inlet of which communicates with a fuel tank and the outlet of which, where during operation a constant pressure is maintained by a pressure control device, communicates with the inlet of a flow restrictor having a passage which can be controlled continuously between the fully opened and the fully closed condition by an electrically controlled operating element, the restrictor outlet communicating with the fuel inlet chamber of a pressure control valve which during operation maintains a constant pressure at the restrictor outlet which is lower than the constant pressure at the restrictor inlet and the fuel outlet chamber of said valve communicates with a fuel distributor which is capable of communicating the various atomizers periodically and per atomizers always for the same time interval with said fuel outlet chamber.

5 Claims, 7 Drawing Figures PAIENIEDAPR 91314 3802.454

SHEEF 1 0F 3 Fig.2

INVENTOR.

WILHELM J. KLE UTERS BY I ATENTEBAPR 9 @974 8024 saw 2 0F 3 RA/WW INVENTOR.

WILHEL'M J. KLEUTERS jaw 3% PATENTEBAPR 9 1974 v 3.302.454

sum 3 0F 3 INVENTOR. WILHELM J-KLEUTERS J 1, ai

The invention relates to a device for supplying fuel to the atomisers of combustion engine comprising a fuel pump the inlet of which communicates with a fuel tank and the outlet of which can be made to communicate with the atomisers; a pressure control device is present for maintaining during operation a constant fuel pressure at the outlet of the pump.

Devices of this type are known from FIG. 1 of the Pat. Nos. 3,240,191 and 3,334,679. Dependent upon the choice of the pump, the pressure control device which ensures that the fuel is supplied under a constant pressure may or may not comprise a pressure buffer vessel (air chamber). The'operation and construction of a pressure buffer vessel are described, for example, in the US. Pat. No. 2,300,722.

In the devices known from the above U.S. paten specifications, an electronically operated magnetic valve is incorporated in the supply line. The amount of fuelto be injected into the cylinder of the engine per work stroke and which is in a given proportion to the amount of air to be drawn in per work stroke is controlled in this case by variation 'of the injection time In order to realize this objective, the device according to the invention is characterized in that at least one flow restrictor is present having a passage which can be controlled continuously between the fully opened and fully closed position by means of an electrically controlled operating element. The restrictor inlet communicates with the outlet of the pump and the restrictor outlet communicates with a first pressure control valve which during operation maintains a constant pressure at the restrictor outlet which is lower than the constant pressure at the restrictor inlet. The first pressure control valve comprises a casing having a fuel inlet chamwith constant fuel supply per unit of time. For that purpose, an electric pulse is supplied to the magnetic valve as-a result of which said valve opens for a short of'time, dependent upon the pulseduration, and fuelcan' flow to the cylinder. Accurate and rapid dosing of fuelis possible in these known devices by using magnetic valves which are operated vice.

Adrawback is, however, that a good mixing of the by an electronic controldedrawn-in quantity of air and the injected amount of fuel the'engine is switched to partial load, a smaller amount of air is drawn-in during the same time interval as with full load. Adaptation of the correspondingly smaller amount of required fuel can now be carried out'only by shortening the injection time since, with the magnetic valve in the open position, a constant amount of fuel passes said valve per unit of time owing to the constant fuel pressure in the supply line. i

if in addition the number of revolutions is reduced,

the quantity of air required per work stroke will be drawn-in in a longer period of time so that an even greater'discrepancy arises between the air drawing-in time and fuel injection time.

As already said, this results in a poor mixing of the air and the fuel and consequently incomplete combustion.

of the mixture as a result of which a lowengine efficiency and dirty exhaust gases which are detrimental to health are obtained. N i

lt is the object of the present invention to provide a device in whichthe said drawback does not occur and the rapid and accurate dosing of the amount of fuel to be supplied to the engine is maintained.

her communicating with the restrictor and a fuel outlet chamber separated from said inlet chamber and between which chambers a valve seat is arranged. A value body is present which is capable of co-operating with the valve seat and is capable of releasing fully or partly the passage thereof. Fuel supplied to the control valve exerts a force on the valve body in a direction away from the valve seating, and resilient means is present which exerts a force on the valve body in the direction of the seat, said means having a small spring constant for providing a flat fuel pressure-flow characteristic of the control valve. Said control is further constructed so that forces exerted on the valve body in a direction away-from the seat as a result of the fuel pressure in the outlet chamber are small relative to those as a result of the fuelpressure in the inlet chamber. The outlet chamber communicates with a fuel distributor which is capable of communicating the various atomisers periodically and per atomiser always for the same time interval with the outlet chamber.

Since during operation constant pressures prevail both onthe inlet side and on the outlet side of the restrictor, and hence a constant pressure differential is present across said restrictor, the amount of fuel flowing towards the control valve can simply and rapidly be controlled by varying the passage of the restrictor by means of an electronic control device. The control valve also ensures that the flow of fuel passed through the restrictor experiences substantially no influence and is independent of pressure variations occurring in the outlet of the control valve. The fuel distributor ensures that the supplied fuel is evenly distributed between the atomisers.

Since the pressure control valve has a flat pressureflow characteristic, a minimum pressure variation occurring at the restrictor outlet as a result of a variation of the fuel flow by variation of the passage of the restrictor, will immediately result in a great variation in the passage of the control valve. Hence the varied flow of fuel is passed without hindrance.

Theadvantage of the-fact that the fuel in the outlet chamber of the pressure control valve can exert only minor forceson the valve body as compared with the forces exerted on said body by fuel in the inlet chamber, isthat pressure variations occurring in the outlet chamber and originating, for example, from the fuel distributor during the alternate switching to the various I atomisers; have only a small influence on the pressure at the restrictor outlet, so that the pressure differential across'the restrictor and hence the flow of fuel passed through the restrictor then remain substantially constant. The supplied flow of fuel therefore is substantially independent -of the pressure variations which occur on the side of the pressure control valve facing the fuel distributor.

However, when the amounts of fuel to be injected are comparatively small, the problem may present itself that the small displacement of the valve body under the influence of the pressure variations in the outlet chamber produces too large a spreading in the amounts of fuel allotted to the atomisers. If, for example, the fuel distributor switches alternately from an atomiser having injection pressure p to an atomiser having injection pressure p A p, the position of the valve body will vary between x and A x. This variation in injection pressure is caused by tolerances in dimensions occurring during the manufacture of the atomisers resulting in variations in the resistance to flow of said atomisers.

When switching from an atomiser having injection pressure p to an atomiser having injection pressure p A p, the displacement of the valve body over the distance A x will produce a volume variation A V.

When the valve body assumes the new position, an

amount of fuel having volume A V is momentarily with drawn from the constant flow of fuel originating from the restrictor, while after said new position has been assumed, the original constant flow of fuel can pass through the pressure control valve without hindrance during the remaining time in which the atomiser with injection pressure p A p communicates with the fuel distributor. When a quantity of fuel of volume V has been supplied to the atomiser having injection pressure p, an amount volume V AV is allotted to the atomiser having injection pressure p A p. In particular in the case of small injection quantities, too large an error in the distribution of the fuel across the various atomisers may arise as a result of this. ln order to avoid this drawback, a favorable embodiment of the device according to the invention comprises a second pressure control valve which is accommodated in the communication between the first pressure control valve and the fuel distributor for maintaining a constant pressure differential between the inlet and outlet chambers of the first pressure control valve, said second pressure control valve comprising a casing having a fuel inlet space communicating with the outlet chamber of the first control valve and a fuel outlet space communicating with the fuel distributor and separated from said inlet space, between which spaces a valve seat is arranged. A valve body is present which is capable of cooperating with the valve seat of the second control valve and is capable of releasing the passage thereof fully or partly and which is capable of varying with its side remote from the valve seat the volume of a further fuel space. This further space is in open communication with the fuel inlet chamber of the first pressure control valve via a communication duct. Fuel supplied to the inlet space of the second pressure control valve exerts on the valve body a force directed away from the valve seat, and at least one resilient element is present which also exerts a force on the valve body which is directed away from the valve seat, and said element having a small spring constant for providing a flat fuel pressure-flow characteristic of the second control valve. The second control is being furthermore constructed so that forces exerted on the valve body in a direction away from the seat as a result of the fuel pressure in the outlet space are small relative to those resulting from the fuel pressure in the inlet space.

If there is switched from an atomiser having injection pressure p to an atomiser having injection pressure p A p, the valve body of the second pressure control valve and that of the first pressure control valve will in the first instance each move away over a given small distance from their associated seating.

The valve body of the second control valve assumes a new position, corresponding to the new injection pressure p A p, which position is maintained for the time that the atomiser having injection pressure p A p communicates with the fuel distributor. When said new position is assumed, a given amount of fuel is momentarily withdrawn from the passing flow of fuel as a result of the volume variation associated with the displacement of the valve body. Simultaneously, however, the same amount of fuel is driven by said valve body out of the further fuel space, via the communication duct, to the inlet chamber of the first control valve and supplied to the flow of fuel passing there.

When the control action is sufficiently rapid the result is that a displacement of the valve body of the second control valve produces no variation in the amount of fuel supplied per atomiser.

After the displacement as a result of the switching of the fuel distributor to the atomiser having injection pressure p A p, the valve body of the first control valve returns again to its original position in that the second pressure control valve, after the control action, again holds the pressure differentiated between the inlet and outlet chambers of the first pressure control valve constant and at the original valve. When the return of the valve body of the first control valve to the original position occurs sufficiently rapidly, the amount of fuel momentarily withdrawn from the passing flow of fuel which is a result of the volume variation associated with the displacement of said valve body will again be allotted to the said flow within the time duration that the atomiser having injection pressure p A p communicates with the fuel distributor. This displacement also, which in this case is a non-permanent displacement then produces no variation in the amount of fuel allotted per atomiser. Since furthermore the total resistance to flow of the two control valves and the communicating atomiser is always constant as a result of the control action, also, the pressure at the restrictor outlet will always remain constant. The flow of fuel originating from the restrictor than is also constant. From this it will be obvious that mutually equal amounts of fuel will always be supplied to the atomisers.

The flat pressure-flow characteristic of the second pressure control valve again ensures that a varied flow of fuel is passed without hindrance.

In order to ensure in all circumstances that oscillations occurring during the control action are attenuated within the time that a given atomiser communicates with the fuel distributor, a favorable embodiment of the present device comprises a damping flow resistor which is incorporated in the communication duct. The amount of fluid supplied per atomiser is than always the same for each atomiser.

A further favorable embodiment of the device according to the invention is characterized in that a fuel outlet duct is present one end of which communicates with the communication between the restrictor and the first pressure control valve and in which outlet duct a further restrictor is incorporated.

This provides the advantage that when the restrictor still passes a leakage flow in the non-energized condition, this can be removed through the outlet duct. With a suitable choice of the further restrictor, the pressure build-up at the inlet of the first control valve will on the one hand not be so large that the opening pressure of said valve is reached and the leakage flow can flow to the atomisers, while on the other hand during normal operation of the device the further restrictor ensures that the greater part of the fuel passed through the restrictor will'flow through the pressure control valve and not through the outlet duct.

According to the invention, the further restrictor may have a passage which is controllable, by means of an operating member, continuously between a fully opened and a fully closed position. In this manner an extra possibility is available for controlling the flow of fuel to the pressure control valve.

According to the invention, the operating member of the further restrictor may be coupled to the operating element of the restrictor in such manner that a reduction of the passage of the restrictor produces an enlargement of the passage of the further restrictor, and conversely an enlargement of the passage of the restrictor results in a reduction of the passage of the further restrictor. The advantage of this is that a great variation in the flow of fuel to the atomisers is obtained by only a small variation in the passage of the restrictor which means a great sensitivity of the device.

In order that the invention may be readily carried into effect, it will now be described in greater detail, by way of example, with reference to the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1, 4 and 5 shows embodiments of the device,

FIG. 2 is an embodiment of an electrically controlled restrictor FIG. 3a. 3b and.3c show a few embodiments of a pressure control valve suitable for use in the device.

DESCRIPTION OF THE PREFERRED EMBODIMENT Reference numeral 1 in FIG. 1 denotes a pump which communicates with its inlet, via a fuel filter 2, with a fuel tank 3 and communicates with its outlet, via an air chamber 4, with the inlet of a restrictor 5 the passage of which can be controlled continuously betweeen the fully opened and the fully closed positions by electric control means. The outlet of the restrictor 5 communicates, via a first pressure control valve 6, with a fuel distributor 7 having a rotor 8 which is coupled to the cam shaft of a combustion engine not shown and which during operation can alternately communicate the outlet of'the first pressure control valve 6 with one of the ducts 9. Atomisers 10, only one of which is shown in the figure, communicate with each duct 9. The situation shown having four ducts 9 and atomisers 10, respectively, relates to a four-cylinder combustion engine.

A return flow duct 11 which is arranged between air chamber 4 and restrictor 5 and which debouches in the fuel tank 3 communicates with the communication between the pump 1 and the restrictor 5. A spring-loaded relief valve 12 is incorporated in said return flow duct.

The operation of the device is as follows: During operation, fuel is pumped by the pump 1 from the fuel tank 3 to the restrictor 5, Air chamber 4 and relief valve 12 together constitute a pressure control device which keeps the pressure at the outlet of the pump and the inlet of the restrictor 5, respectively, constant at a given value. Any excess of fuel supplied by the pump 1 flows via the relief valve 12 back to the fuel tank 3.

The first pressure control valve 6 ensures that the pressure of the fuel passed through the restrictor 5 is kept constant at a given value at the restrictor outlet, which constant pressure is lower than the constant pressure at the inlet of the restrictor. So a constant pressure differential prevails across the restrictor. The flow of fuel which has passed the first pressure control valve 6 is evenly distributed by the fuel distributor 7 between the various atomisers in that the flow of fuel is supplied to each atomiser 10 alternately for the same time interval. The amounts of fuel supplied to the atomisers are then mutually equal. If the flow of fuel is to be changed, an electric signal is supplied to restrictor 5 by means of a control apparatus (not shown) which reacts,for example, to a variation in the quantity of air drawn-in by the engine, as a result of which the passage of said restrictor is varied to the desired extent.

Since a constant pressure differential prevails across the restrictor 5, the variation in the flow of fuel to the fuel distributor 7 only depends upon the variation in passage of the restrictor. This is of great advantage, since, owing to the electric control, the passage of the restrictor and hence the flow of fuel can be very rapidly varied, this in contrast with devices in which the flow of fuel is varied by varying the fuel pressure with all the mass inertia effects involved.

Since the rotor of the fuel distributor is coupled to the cam shaft of the combustion engine, the injection time of the fuel, irrespective of the number' of revolutions, always remains equal to and remains coinciding with the drawing-in time of the air of combustion which ensures a good mixing in all circumstances, while the amount of fuel per cylinder always is in the correct proportion to the quantity of air of combustion supplied per cylinder in that the flow of fuel is always adjusted to the correct value and a proportional part of said flow is supplied to each atomiser. All this results in an optimum combustion of the readily mixed air and fuel and as a result of this a good engine efficiency as well as clean combustion gases.

The first pressure control valve 6 is constructed so as to have a flat pressure-flow characteristic, that is to say a small variation in the pressure differential across the valve, for example, by a small variation of the pressure at the valve inlet, involves a great variation in the flow of fuel passed through the valve. This means that upon variation of the flow of fuel anew flow passes through the valve without hindrance. Furthermore, the first control valve 6 is constructed so that pressure variations at the outlet of the valve can substantially not influence the pressure at the inlet side of said valve which is of great importance. Actually for example, when the fuel distributor 7 switches from an atomiser having injection pressure p to an atomiser having injection pressure p A p if the pressure variation at the outlet of the pressure control valve 6 would result in a variation in pressure at the input of said valve, then this means that the pressure at the restrictor outlet is varied and hence also the pressure differential across the restrictor. As a result of this, the flow of fuel supplied to the fuel distributor and passed through the restrictor would experience variations which, of course, is undesirable, since in that case mutually different amounts of fuel are allotted to the atomisers.

The way in which the first control valve 6 can be constructed to fulfil the two above-mentioned requirements is shown in FIG. 3 with reference to three embodiments which will be described as the description proceeds.

FIG. 2 shows an embodiment of an electrically controlled restrictor having a passage which can be varied continuously between the fully opened and fully closed position as it can be used in the device shown in FIG. 1. In this figure, reference numeral denotes a casing having an inlet space 16 and an outlet space 17 between which a seat 18 is present the passage of which can be closed and be released more or less, respectively, by a closing element 19 which forms part of an operating element 20. The operating element 20 can be moved more or less to the left and thus release more or less the passage by a stronger or lesser energisation of the electro-magnet 21 having electric conductors 22'. In the non-energized condition of the electromagnet 21, closing element 19 bears against the seating 18 and the communication between the inlet space 16 and the outlet space 17 is interrupted. This is carried out by means of a resilient diaphragm 22 which is connected on one side to the casing 15 and on the other side to the operating element 20 and which also separates the inlet space 16 from a space 23 which, via a duct 24, is in open communication with the outlet space 17. A slack diaphragm 26 provided with apertures is furthermore present in the outlet space 17 and is connected on one side to the casing 15 and on the other side to the operating element 20 and which serves for straight guiding the operating element.

Since the space 23 is in open communication with the outlet space 17, the outlet pressure will prevail on the left-hand side of the diaphragm 22, while on the righthand side thereof the inlet pressure prevails. The result is a force which is directed to the left on said diaphragm and hence on the operating element 20. In the same manner, a force which is directed to the right and is proportional to the difference between the inlet and outlet pressures is excerted on the closing element 19.

By suitable choice of the cross-sections of the diaphragm 22 and the closing member 19 it is achieved that the said forces compensate each other. This means that the position of the operating element 20 is independent of the pressure differential prevailing across the restrictor.

The pressure control valve shown in FIG. 3a consists of a casing 30 having an inlet chamber 31 and an outlet chamber 32 between which a valve seat 33 is arranged the passage 34 of which can be released more or less and be closed, respectively, by a valve body 35 which communicates with a piston-like body 37 via a valve stem 36. A compression spring 38 is furthermore present which exerts a force on the assembly of piston-like member 37, valve stem 36 and valve body 35 in the direction of the valve seat 33 and which compression spring has a small spring constant (slack spring). Atmospheric pressure prevails in the space 39. At the lower side of the piston-like body 37, fuel supplied to the inlet chamber 31 exerts a force on said body which tends to displace the assembly of piston-like member 37, valve stem 36 and valve body 35 in the direction away from the valve seating 33.

A small variation in the fuel pressure in the inlet chamber results in a comparatively large displacement of the assembly and hence a comparatively large variation in the passed flow of fuel due to the slackness of the compression spring 38.

Owing to the large surface area of the piston-like body 37 which is subject to the fuel pressure in the inlet chamber 31 as compared with the effective surface area of the valve body 35, the fuel pressure in the outlet chamber 32 plays substantially no significant part in the play of forces on the assembly and a variation in the fuel pressure in the outlet chamber has substantially no influence on the pressure in the inlet chamber. All this is of great importance, as already said, for reasons of constancy of the flow of fuel.

In the pressure control valve shown in FIG. 3b, components corresponding to FIG. 3a are referred to by the same reference numerals where appropriate, but with a prime added. Valve stem 36 comprises bores 40. After having passed through the bores 40, fuel supplied to the inlet chamber 31 can exert a force on a diaphragm 41 in a direction away from the valve seat 33'. Compression springs 38 constructed as cup springs having a small spring constant exert a force on said diaphragm in the direction of the seat 33. A compre'ssion spring 42 ensures that the assembly of valve body 35' and valve stem 36 remains pressed against the diaphragm 41.

In this case also it is ensured by a large effective surface area of the diaphragm 41 as compared with the effective cross-section of the valve body 35 that pressure variations in the outlet chamber 32 have substantially no influence on the pressure in the lnlet chamber 31'.

In the pressure control valve shown in FIG. 30 components corresponding to FIG. 3a are also referred to by the same reference numerals where appropriate, but with a double prime added. In this embodiment, a valve body 35 is constructed in the form of a piston and is secured to the casing 30 via a bellows 45. Compression spring 38" is accommodated inside the valve body 35"and bellows 45.

Fuel in the outlet chamber 32" can in this case substantially only exert forces on the cylinder surface of the valve body 35", which forces are radially directed inwards, and which forces leave the axial movement of the valve body unhindred. Pressure variations in the outlet chamber therefore have substantially no influence on the pressure in the inlet chamber in this case also.

The device shown in FIG. 4 in general is equal to that shown in FIG. 1 which is way similar reference numerals with a added used for corresponding components where appropriate. The only difference is that in the present case there is accommodated between the first pressure control valve 6a and the fuel distributor 7a a second pressure control valve 50 having a casing 51, a valve body 52, a fuel inlet space 53 and a fuel outlet space 54 between which a valve seating 55 is arranged and a further fuel space 56 the volume of which can be varied by the valve body 52 with its side remove from the valve seating 55 formed by a piston-like part 57. Between the valve seating 55 and the piston-like part 57 of the valve body 52 is present a compression spring 58 of small spring constant which exerts a force on the part 57 in a direction away from the seating. For convenience, the same-reference numerals (witha added) are used for the first pressure control valve 6a for components which correspond to those of FIG. 3a.

Fuel outlet chamber 32a of the first pressure control valve 6a is in open communication with fuel inlet space 53 of the second pressure control valve 50, while further fuel space 56 of the second pressure control valve 50 is in open communication, via a communication duct 59, with fuel inlet chamber 31a of the first pressure control valve 6a. A damping flow resistor60 is incorporated inthe communication duct 59. As compared with the device shown in FIG. 1, this device pres ents the following advantage. When the fuel distributor of the device shown in FIG. 1 switches from an atomiser having injection pressure p to an atomiser having injection pressure p A p, the assembly of valve body 35a, valve stem 36a and piston-like member 370 (see FIG. 3a) will move upwards and assume a new position as a result of the increase in pressure in'the fuel outlet chamber 32a of the first pressure control valve 6a. This is associated with an increase in volume of the fuel inlet chamber 31a. As a result of this an amount of fuel is momentarily withdrawn from the constant flow of fuel supplied to the inlet chamber 32a and originating from the restrictor 5, which amount has a volume which corresponds to the volume variation A V of inletchamber 31a. After the assembly has assumed thenew position, the original constant flow of fuel again passes the first pressure control valve without hindrance. When an amount of fuel of volumen V was allotted to the atomiser having injection pressure p, the atomiser having injection pressure p A p receives an amount of volume V A V. When comparatively small amounts of fuel, so with small V, are supplied to the atomisers, A V may mean too large a mutual difference in the amounts of fuel supplied to the various atomisers. In the device shown in FIG. 4 this drawback is no longer present.

When there is switched from an atomiser having injection pressure p to an atomiser having injection pressure p A p,-in the first instance valve body 52 of the second pressure control valve 50 and valve body 35 of the first pressure control valve 6a move away from there respective valve seatings 55 and 33a.

ation from the flow of fuel passing through said space (on its way to the fuel distributor 7). The piston-like part 57 of the valve body 52, however, at the same time displaces the same volume of fuel from the fuel space 56 via duct 59 to fuel inlet chamber 31a of the first pressure control valve 6a, which fuel is supplied to the flow of fuel which passes'there and is on its way to the second pressure control valve 50.

fuel suppliedto the atomiser having injection pressure p A p in that casedoesnot differ from the amount supplied to the atomiser having injection p and is not influenced by the displacement of the valve body 52 of the second pressurecontrol valve 50 occurring during the switching. Valve body a of the first pressure control valve 6a returns to its original position since after the control action of the second pressure control valve the latter again keeps the differential pressure between the inlet chamber 3 1a and outlet chamber 32a of pressure control valve 6 constant at the original value. Bysuitable proportioning, the return to the original position will occur rapidly so that the amount of fuel momentarily withdrawn from the flow of fuel passing the inlet chamber 31a as a result of the displacement of the assembly valve body 35a, valve stem 36a and piston like body 37a, is. again supplied to said flow and reaches the atomiser having injection pressure, p

A p before the communication between said atomiser andthe fuel distributor is interrupted. The momentary displacement of valve body 350 of the first pressure control valve 6a then also produces no variation in the amount of fuel supplied per atomiser.

Damping flow resistor ensures that oscillations of the system of control valves are damped sufficiently rapidly to supply the desirable amount of fuel to a given atomiser'within the period of time in which said atomiser communicates with the fuel distributor.

Owing to the displacement of valve body 35a of the first pressure control valve 6a, the pressure at the outlet of restrictor 5a remains constant during the control action and hence also the flow of fuel originating from the restrictor. After the control action, at least for the rest of thetime in which the atomiser having injection pressure p A p communicates, a stationary condition has established with a permanent deviation from the original position for valve body 52 and with the original position for valve body 35a. The switching to an atomiser having a higher resistance to flow has had for its result a larger passage and therefore smaller resistance to flow of the second pressure control valve 50 in such manner that the overall resistance to flow between the outlet of restrictor 5a and the outlet of the atomiser has remained constant. The pressure at the restrictor outlet and hence the flow of fuel originating from the restrictor 5a has remained constant also after the control action.

In this manner it is achieved that when switching to atomisers having mutually different resistances to flow, always equal quantities of .fuel from a constant flow of fuel are supplied to the atomisers mutually.

TI-Ie valve body 35a of thefirstpressure control valve 6a will assume a permanent new position only upon variation of the passage of restrictor 5a.

Inorder to ensure that fuel pressure variations occurring in the fuel outlet space 5.4 as a result of the switchings of the fuel distributor have substantially no influ- By suitable proportioning it is achieved that the sam amount of fuel as is withdrawn momentarily from the flow of fuel in inlet space 53 as a result of the displacement of the valve body 52 is'supplied again to said flow and has reached the fuel distributor 7a within the time in which the atomiser having injection pressure p +,A p communicates with the distributor. The amount of ence on the pressure in the inlet space 53 and outlet chamber 320, respectively, the control valve 50 is constructed so that fuel in the outlet space 54 can exert only mirror forces on the valve body 52 as compared to those whichare exerted on said body by fuel in the inlet space 53. correspondingly, the comparatively large surface area of the piston-like part 57 in FIG. 4 is, subject to. the fuel pressure in the inlet space 53. Of course, all kinds of other embodiments of the second pressure control valve 50 are possible, for example,

mainly constructed in analogy with the pressure control valves as shown in FIGS. 3b and 3c.

For the device shown in FIG. 5, similar reference numerals (with b added) are used for components corresponding to H0. 4. where appropriate. The device shown in FIG. differs from that shown in FIG. 4 only in that in the present case a fuel outle duct 65 communicates with the communication between the restrictor 5b and the first pressure control valve 6b, which outlet duct with its other end debouches in fuel tank 31) together with the return flow duct 11b.

A further restrictor 66 the passage of which can be controlled continuously between the fully opened and fully closed position is incorporated in the fuel outlet duct 65. The further restrictor 66 is coupled, via a coupling 67 not shown in detail, to restrictor 5bin such manner that, when the passage of restrictor 5b is reduced, the passage of the further restrictor 66 is enlarged, and conversely. The further restrictor 66 may be constructed, for example, as the restrictor shown in H0. 2 without an electromagnet. If in this case the re strictor 5b is constructed as shown in FIG. 2, the operating elements b may be coupled together.

Due to the presence of fuel outlet duct 65, in the case of leakage of restrictor 5b in the non-energized condition, the leakage flow can be returned to the fuel tank 312 without the danger of a pressure build-up at the inlet of the pressure control valve 6b that could result in opening of said valve so that fuel could reach the atomisers.

The further restrictor 66 makes the device more sensitive because during operation a small variation in the passage of restrictor 5b produces a large variation in the flow of fuel to the atomisers.

In the embodiments of the device described, four atomisers are present which are each connected separately to the fuel distributor. It is of course also possible to connect, for example, 6b, 8b, 12b and so on atomisers, either each time one, or several at a time.

What is claimed is:

1. Apparatus operable with a combustion engine wherein a fuel pump of the engine discharges via its outlet, fuel pumped from a tank through said apparatus to atomizers to the engine, the apparatus comprising: a pressure control device for maintaining constant fuel pressure at said pump outlet, a flow restrictor including a flow passage having an inlet communicating with said pump outlet and an outlet, said passage being variable between open and closed conditions, electric controlled means for varying said restrictor passage opening, a fuel distributor directing fuel to said atomizers, a first pressure control valve for maintaining pressure at said restrictor outlet lower than pressure at said restrictor inlet, said control valve including a casing having fuel inlet and outlet chambers separated by a valve and valve seat, the inlet chamber communicating with said restrictor outlet, the outlet chamber communicating with said distributor, and resilient means having a low-magnitude spring constant urging said valve to be closed according to a flat pressure-flow characteristic, whereby fuel flowing into said valve inlet chamber exerts a force on said valve therein tending to unseat same, and fuel pressure in the outlet chamber tends to open valve and is small relative to fuel pressure in the inlet chamber and tends to open the valve, said appara tus further comprising: a second pressure control valve for maintaining a constant pressure differential between said inlet and outlet chambers of said first pressure control valve, said second control valve comprising a casing, separate fuel inlet and outlet spaces within the casing, a valve and seat separating said spaces, the inlet and outlet spaces respectively communicating with said first valve outlet chamber and with said distributor, said second control valve casing further defining therein a further fuel space of volume variable by the valve thereof, and including resilient means having small magnitude spring constant tending to unseat said valve according to a flat fuel pressure flow characteristic, said apparatus further comprising a communication duct in open communication between said fuel inlet chamber of said first valve and said further space, whereby fuel entering said second valve inlet chamber exerts a force tending to unseat said valve therein, and fuel pressure in the outlet chamber also tends to unseat said valve, this pressure being small relative to pressure in the inlet chamber which also tends to unseat said valve.

2. Apparatus according to claim 1 further comprising a damping flow resistor incorporated in said communication duct.

3. Apparatus according to claim 1 further comprising a fuel outlet duct having one and connecting between said resistor outlet and said first valve inlet, and a discharge end, and a further restrictor incorporated in said fuel outlet duct.

4. Apparatus according to claim 3 wherein said further resistor has a flow passage therethrough, further comprising means for varying said flow passage between open and closed conditions.

5. Apparatus according to claim 3 wherein said means for varying the flow passages of said restrictors,

opens one and closes the other proportionately. 

1. Apparatus operable with a combustion engine wherein a fuel pump of the engine discharges via its outlet, fuel pumped from a tank through said apparatus to atomizers to the engine, the apparatus comprising: a pressure control device for maintaining constant fuel pressure at said pump outlet, a flow restrictor including a flow passage having an inlet communicating with said pump outlet and an outlet, said passage being variable between open and closed conditions, electric controlled means for varying said restrictor passage opening, a fuel distributor directing fuel to said atomizers, a first pressure control valve For maintaining pressure at said restrictor outlet lower than pressure at said restrictor inlet, said control valve including a casing having fuel inlet and outlet chambers separated by a valve and valve seat, the inlet chamber communicating with said restrictor outlet, the outlet chamber communicating with said distributor, and resilient means having a low-magnitude spring constant urging said valve to be closed according to a flat pressure-flow characteristic, whereby fuel flowing into said valve inlet chamber exerts a force on said valve therein tending to unseat same, and fuel pressure in the outlet chamber tends to open valve and is small relative to fuel pressure in the inlet chamber and tends to open the valve, said apparatus further comprising: a second pressure control valve for maintaining a constant pressure differential between said inlet and outlet chambers of said first pressure control valve, said second control valve comprising a casing, separate fuel inlet and outlet spaces within the casing, a valve and seat separating said spaces, the inlet and outlet spaces respectively communicating with said first valve outlet chamber and with said distributor, said second control valve casing further defining therein a further fuel space of volume variable by the valve thereof, and including resilient means having small magnitude spring constant tending to unseat said valve according to a flat fuel pressure flow characteristic, said apparatus further comprising a communication duct in open communication between said fuel inlet chamber of said first valve and said further space, whereby fuel entering said second valve inlet chamber exerts a force tending to unseat said valve therein, and fuel pressure in the outlet chamber also tends to unseat said valve, this pressure being small relative to pressure in the inlet chamber which also tends to unseat said valve.
 2. Apparatus according to claim 1 further comprising a damping flow resistor incorporated in said communication duct.
 3. Apparatus according to claim 1 further comprising a fuel outlet duct having one end connecting between said resistor outlet and said first valve inlet, and a discharge end, and a further restrictor incorporated in said fuel outlet duct.
 4. Apparatus according to claim 3 wherein said further resistor has a flow passage therethrough, further comprising means for varying said flow passage between open and closed conditions.
 5. Apparatus according to claim 3 wherein said means for varying the flow passages of said restrictors, opens one and closes the other proportionately. 